1. Field of the Invention
The invention relates generally to an offshore riser tensioner assembly. More specifically, the invention relates to pull up riser tensioner having a rod with a piston that telescopes within a cylinder, the pull-up force being applied from pressure in an annulus surrounding the rod.
2. Description of Related Art
Risers are used for offshore oil and gas wells to connect the subsea wellhead to the topside equipment on a floating production platform. Typically, a riser system is employed to provide a conduit from a floating vessel at the water surface where the blowout preventer (BOP) stack or production tree is located down to the wellhead at the sea floor.
Tensioners are employed at the platform to apply tension to the risers. A tensioning system maintains a variable tension to the riser string, thereby alleviating the potential for compression, which can lead to buckling or failure of the risers. Another purpose of a tensioner is to serve as a motion compensator. A tensioner that is coupled to riser string can compensate for vessel motion inducted by wave action and heave.